The present disclosure relates generally to delivery devices and a method for forming the same.
Parathyroid hormone (PTH) is a peptide hormone that is capable of exhibiting either anabolic or catabolic effects on bone, depending, at least in part, on the dosage and delivery pattern. Generally, a continuous high dose delivery of PTH leads to catabolic effects, while a continuous low dose or a pulsatile high dose delivery of PTH results in anabolic effects on bone. Daily injections may be an anabolic treatment, however, such treatment is less convenient and may not be favorable to patients. As such, controlled delivery of PTH, and other like substances, in an anabolic fashion is highly desirable.
Attempts have been made to devise a successful system for pulsatile substance release. Such systems may be classified as stimulus-induced pulsatile release systems or self-regulated pulsatile release systems. In stimulus-induced delivery systems, drugs are triggered to release by external stimuli, such as temperature, pH, light, enzymes, electric and magnetic fields, and/or combinations thereof. While these stimulus-responsive devices have shown promising pulsatile release characteristics, many of the stimuli are not suitable or preferable for use in patients. In addition, most of the systems in this category are constructed using non-biodegradable polymers.
In self-regulated pulsatile release systems, drugs are usually encapsulated within a barrier material, which is often composed of an erodible or biodegradable polymer. After the barrier material is dissolved, eroded or degraded, the drugs are rapidly released from the inner reservoir core. These systems are usually biocompatible and biodegradable, but multiple barriers or coatings may be required to achieve the desired multiple pulses of release. Multiple layers may, however, pose challenges in material properties and device fabrication technologies, often resulting in inconsistency.
Other attempts to devise a successful system for pulsatile substance release have included combining the self-regulated release reservoir design with a microfabrication technique. Disk-shaped biodegradable polymeric chips have been fabricated to achieve multi-pulse drug release. While this device may be useful, the reservoirs in the device are arranged parallel to each other, which potentially wastes space and limits the miniaturization capacity.